Components of a Transformer
Basic Parts of a Transformer
These are the
basic components of a transformer.
1.
Laminated core
2.
Windings
3.
Insulating materials
4.
Transformer oil
5.
Tap changer
6.
Oil Conservator
7.
Breather
8.
Cooling tubes
9.
Buchholz Relay
10.
Explosion vent
1.
Core
The core acts as support to the winding in the
transformer. It also provides a low reluctance path to the flow of magnetic
flux. It is made of laminated soft iron core in order to reduce eddy current
loss and Hysteresis loss. The composition of a transformer core depends on such
as factors voltage, current, and frequency. The diameter of the transformer
core is directly proportional to copper loss and is inversely proportional to
iron loss. If the diameter of the core is decreased, the weight of the steel in
the core is reduced, which leads to less core loss of the transformer and the
copper loss increase. When the diameter of the core is increased, the vise
versa occurs.
2.
Why Are Windings Made of
Copper?
· Copper has high conductivity. This minimizes losses as well as the
amount of copper needed for the winding (volume & weight of winding).
· Copper has high ductility. This means it is easy to bend conductors
into tight windings around the transformer's core, thus minimizing the amount
of copper needed as well as the overall volume of the winding.
2.1 Winding
Two sets of winding are made over the transformer core and are
insulated from each other. Winding consists of several turns of copper
conductors bundled together, and connected in series.
· Winding can be classified in two different ways:
· Based on the input and output supply
· Based on the voltage range
Within the input/output supply classification, winding are further
categorized:
· Primary winding - These are the winding to which the input voltage
is applied.
· Secondary winding - These are the winding to which the output
voltage is applied.
Within the voltage range classification, winding are further
categorized:
· High voltage winding - It is made of copper conductor. The number of
turns made shall be the multiple of the number of turns in the low voltage
winding. The conductor used will be thinner than that of the low voltage
winding.
· Low voltage winding - It consists of fewer number of turns than the
high voltage winding. It is made of thick copper conductors. This is because
the current in the low voltage winding is higher than that of high voltage
winding.
Input supply to the transformers can be applied from either low
voltage (LV) or high voltage (HV) winding based on the requirement.
3.
Insulating Materials
Insulating paper and cardboard are used in
transformers to isolate primary and secondary winding from each other and from
the transformer core.
4.
Transformer oil
It is another insulating
material. Transformer oil performs two important functions: in addition to insulating
function, it can also cool the core and coil assembly. The transformer's core
and winding must be completely immersed in the oil. Normally, hydrocarbon
mineral oils are used as transformer oil. Oil contamination is a serious
problem because contamination robs the oil of its dielectric properties and
renders it useless as an insulating medium.
5.
Tap Changer
The output voltages of transformers vary according to
its input voltage and the load. During loaded conditions, the voltage on the
output terminal decreases, whereas during off-load conditions the output
voltage increases. In order to balance the voltage variations, tap changers are
used. Tap changers can be either on-load tap changers or off-load tap changers.
In an on-load tap changer, the tapping can be changed without isolating the
transformer from the supply. In an off-load tap changer, it is done after
disconnecting the transformer. Automatic tap changers are also available.
6. Transformer Tank
It is the outer container of the Transformer inside which the CORE
and WINGDINGS are inserted and filled with OIL. Also on top of the tank,
bushings, terminals etc are provided. The material used is mainly thin sheet
steel properly welded to avoid leakage of OIL.
7.
BUSHINGS
A bushing is an insulated device that allows an
electrical conductor to pass safely through a grounded conducting barrier such
as the body of the transformer (Tank). Bushings are typically made from
porcelain, though other highly insulating materials are also used
They are located on the top portion of the Transformer Tank both on
High Voltage side and Low voltage side.
A
bushing must be designed to withstand the electrical field strength produced in
the insulation, when any earthed material is present. As the strength of the
electrical field increases, leakage paths may develop within the insulation. If
the energy of the leakage path overcomes the dielectric strength of the
insulation, it may puncture the insulation and allow the electrical energy to
conduct to the nearest earthed material causing burning and arcing.
Conservator
The conservator conserves the transformer oil. It is
an airtight, metallic, cylindrical drum that is fitted above the transformer.
The conservator tank is vented to the atmosphere at the top, and the normal oil
level is approximately in the middle of the conservator to allow the oil to
expand and contract as the temperature varies. The conservator is connected to
the main tank inside the transformer, which is completely filled with
transformer oil through a pipeline.
Breather
The breather controls the moisture level in the
transformer. Moisture can arise when temperature variations cause expansion and
contraction of the insulating oil, which then causes the pressure to change
inside the conservator. Pressure changes are balanced by a flow of atmospheric
air in and out of the conservator, which is how moisture can enter the system.
If the insulating oil encounters moisture, it can
affect the paper insulation or may even lead to internal faults. Therefore, it
is necessary that the air entering the tank is moisture-free.
The transformer's breather is a cylindrical container
that is filled with silica gel. When the atmospheric air passes through the
silica gel of the breather, the air's moisture is absorbed by the silica
crystals. The breather acts like an air filter for the transformer and controls
the moisture level inside a transformer. It is connected to the end of breather
pipe.
Cooling Tubes
Cooling tubes are used to cool the transformer oil.
The transformer oil is circulated through the cooling tubes. The circulation of
the oil may either be natural or forced. In natural circulation, when the
temperature of the oil rises the hot oil naturally rises to the top and the
cold oil sinks downward. Thus the oil naturally circulates through the tubes.
In forced circulation, an external pump is used to circulate the oil.
Buchholz Relay
The Buchholz Relay is a protective device container housed over the
connecting pipe from the main tank to the conservator tank. It is used to sense
the faults occurring inside the transformer. It is a simple relay that is
operated by the gases emitted during the decomposition of transformer oil
during internal faults. It helps in sensing and protecting the transformer from
internal faults.
Explosion Vent
The explosion vent is used to expel boiling oil in the
transformer during heavy internal faults in order to avoid the explosion of the
transformer. During heavy faults, the oil rushes out of the vent. The level of
the explosion vent is normally maintained above the level of the conservatory
tank.
No comments:
Post a Comment